Wireless personal local area network

ABSTRACT

A transceiver apparatus for creating a wireless personal local area network between a computer terminal and one or more peripheral devices. A separate transceiver is connected to the computer terminal and to each peripheral device. The transceivers can be connected to the terminal or peripheral device either internally or externally. A low power radio is used to communicate information between the computer terminal and peripheral devices. Different transceivers can be used for modifying the carrier frequency and power of the local area network. The microprocessor is located inside each transceiver and controls the information flow of the transceiver including the communication protocol which allows each device to know if other devices are communicating, which devices are being communicated to, and selectively address the peripheral devices. An Idle Sense communication protocol is used for information transfer between the computer terminal and the peripheral devices, increasing efficiency in power management and compensating for transmission collisions.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of application Ser. No.08/959,432 filed Oct. 28, 1997, now (U.S. Pat. No. ______ issued Mar.19, 2002), which is a continuation of U.S. application No. 08/500,977filed Apr. 4, 1996, (now U.S. Pat. No. 5,682,379 issued Oct. 28, 1997),which is the U.S. national stage entry of PCT Application No.PCT/US93/12628 filed Dec. 23, 1993, (published as WO94/15413 on Jul. 7,1994). The Application No. PCT/US93/12628 claims priority to U.S.application Nos. 08/027,140 filed Mar. 5, 1993 (now U.S. Pat. No.5,602,854 issued Feb. 11, 1997), and Ser. No. 07/997,693 filed Dec. 23,1992 (now abandoned). Said application No. 08/500,977 is a continuationin part of said application No. 08/027,140, which is a continuation inpart of said application No. 07/997,693, which is a continuation-in-partof application No. 07/982,292 filed Nov. 27, 1992, (now abandoned).

BACKGROUND OF THE INVENTION

Computer terminals and peripheral devices are now used in practicallyevery aspect of life. Computer terminals come in all shapes and sizesand vary greatly in terms of function, power and speed. Additionally,the number of peripheral devices which can be attached to the computerterminals is increasing. Many peripheral devices exist such as printers,modems, graphics scanners, text scanners, code readers, magnetic cardreaders, external monitors, voice command interfaces, external storagedevices, and so on.

Computer terminals and peripherals have become dramatically smaller andmore portable. Personal computers and peripherals are small enough tosit on the desk at work. Smaller still are lap top computers andnotebook computers. There are computer terminals which are small enoughto be mounted in a vehicle such as a delivery truck or on a fork lift.Still smaller are the hand held terminals typically used for theirportability features where the user can carry the computer terminal inone hand and operate it with the other.

Despite the reduction in computer size, the computer terminal still mustphysically interface with the peripheral devices. Thus, there musteither be a cable running from one of the computer terminal to eachdevice or the computer terminal must be docked with the device while theinformation transfer is to take place.

In the office or work place setting, the physical connection istypically done with cables. These cables pose several problems. If thereare many peripheral devices, there must be many cables attached to thecomputer terminal. In addition to the eyesore created by all of thecables, the placement of the peripheral devices is limited by the lengthof the cable. Longer cables can be used but they are costly and do notalleviate the eyesore created by having cables running in alldirections. Additionally, there may be a limited number of ports on thecomputer terminal thus limiting the number of peripherals that can beattached.

Another problem exists when there are several computer terminals whichmust share the same peripheral device such as a printer. All of thecomputers must be hardwired to the printer. As discussed above, longcables can fix this problem at least from a physical connectionperspective but there still remains a protocol problem between thedifferent computers. This problem is especially severe when the variouscomputers are of different types such as a mixed environment of IBM'sand Macintoshes.

In the smaller computer terminal setting, the hand-held terminals andthe potables, the cabling and connection problem can be more severe andcumbersome. Peripheral devices such as printers and scanners of alltypes have been reduced dramatically in size to match the smallness ofthe computer terminals. A notebook computer operator may wish to carrythe computer and a cellular phone modem in a briefcase. Similarly, anoperator may wish to have a hand-held computer terminal in one hand, asmall portable printer attached to his belt, and a code reader in theother hand. The smallness of the computers and peripherals makes thesedemands possible but the required cabling makes these demands costly,inconvenient and even dangerous.

Physically connecting the computer terminals and peripherals severelyreduces the efficiency gained by making the units smaller. An operatormust somehow account for all of the devices in a system and keep themall connected. This can be very inconvenient. In the notebook computerand modem example, the operator may wish to have freedom to move aroundwith the computer but without the modem. He may, for example, wish towork in various locations on a job sight and at various times transmitor receive information via his modem. If the modem and the computer arehard wired together, he must either carry the modem with him at all timeor connect it and then disconnect it each time he wishes to use themodem. Similarly, the operator of the hand held terminal, code readerand printer will have the feeling of being all tied up while using thethree devices simultaneously when all three devices are connected withcables.

The physical connections created by cabling can be expensive becausecables frequently prove to be unreliable and must be replacedfrequently. In portable environments, cables are subject to frequenthandling, temperature extremes, dropping and other physical trauma. Itis not uncommon for the cables or the connectors for the cables on thedevices to need replacing every three months or so. Additionally, all ofthe cabling can be dangerous. An operator who is using, holding orcarrying several devices and feels all tied up is not justinconvenienced, he may be severely limited in his mobility andflexibility as he moves about the work area. This loss of mobility andflexibility directly undercuts the entire reason for having small andportable computers and peripheral devices and greatly increases thelikelihood of operator injury while using the computer and peripheraldevices.

Furthermore, as the cables wear out and break, which, as mentioned,happens frequently, there are dangers which are associated with theelectrical current running through the cables. If the cable orconnectors break, the current could shock the operator or create a sparkwhich could cause a fire or even an explosion in some work environments.

Attempts to alleviate or eliminate these problems have been made buthave not been greatly successful. one solution is to incorporate acomputer terminal and all of the peripherals into one unit. However,this solution proves unsatisfactory for several reasons. For example,the incorporation of many devices into one unit greatly increases thesize and weight, thus jeopardizing the portability of the unit.Furthermore, incorporating all of the functions into one unit greatlyreduces and, in most cases eliminates, the flexibility of the overallsystem. A user may only wish to use a hand-held computer terminal attimes, but at other times may also need to use a printer or occasionallya code reader. An all-incorporated unit thus becomes either overly largebecause it must include everything, or very limiting because it does notinclude everything.

Another solution has been to set up Local Area Networks (LAN's)utilizing various forms of RF (Radio Frequency) communication. The LAN'sto date, however, have been designed for large scale wirelesscommunications between several portable computer terminals and a hostcomputer. Therein, the host computer, itself generally a stationarydevice, manages a series of stationary peripherals that, upon requeststo the host, may be utilized by the portable terminals. Other largescale wireless communications have also been developed which for RFcommunication between several computer terminals and peripheral devices,but all proving to be ineffective as a solution. For example, thesesystems require the peripheral devices to remain active at all times tolisten for an occasional communication. Although this requirement may beacceptable for stationary peripheral devices receiving virtuallyunlimited power (i.e., when plugged into an AC outlet), it provesdetrimental to portable peripherals by unnecessarily draining batterypower. Similarly, in such systems, the computer terminals are alsorequired to remain active to receive an occasional communication notonly from the other terminals or the host but also from the peripherals.Again, often unnecessarily, battery power is wasted.

In addition, such large scale systems are designed for long range RFcommunication and often required either a licensed frequency or must beoperated using spread spectrum technology. Thus, these radios aretypically cost prohibitive, prove too large for convenient use withpersonal computers and small peripheral devices, and require a greatdeal of transmission energy utilization.

Thus, there is a need for a radio frequency communication network thatsupports the use of network peripherals which solves the foregoingproblems relating to power conservation and portability.

SUMMARY OF THE INVENTION

The present invention solves many of the problems inherent The mobilenetwork device participates as a slave to the first network pursuant tothe first protocol and as a master to the second network pursuant to thesecond protocol, and resolves conflicts between the first and secondprotocols in communication systems having devices which use batterypower. The present invention relates generally to local area networksand, more specifically, to a communication system for maintainingconnectivity between devices on networks which have different operatingparameters while limiting the power drain of battery powered devices.

In one embodiment of the present invention, a mobile network device hasa single radio unit which is capable of participating in a first andsecond radio network which operate using a first and secondcommunication protocol. The mobile network device participates as aslave to the first network pursuant to the first protocol and as amaster to the second network pursuant to the second protocol, andresolves conflicts between the first and second protocols.

In another embodiment of the present invention, a mobile network devicehas a first radio transceiver for communicating with a main radionetwork and a second radio transceiver for communicating with a radiosubnetwork. The mobile network device participates as a slave to themain radio network and participates as a master to the radio subnetwork.

In a further embodiment of the present invention, a mobile networkdevice has a single radio unit capable of participating in a first and asecond radio network. The first and second radio networks operate usinga first and second communication protocol, respectively. The mobilenetwork device participates as a slave to the first network pursuant tothe first protocol and as a master to the second network pursuant to thesecond protocol, enters a state of low power consumption when notcommunicating with either the first or second network.

In another embodiment of the present invention, an RF local area networkcontains a first network device which uses battery power to transmitdata to a second network device. In order to conserve power, the secondnetwork device determines a range value between the first and secondnetwork devices and transmits that value to the first network device sothat the first network device can identify an appropriate, andpotentially lower, data rate for subsequent transmission of data. Thefirst network device may also consider its own battery parameters alongwith the received range value and identify an appropriate power level aswell as data rate for subsequent transmissions.

In another similar embodiment, the second network device determines therange value between the first and second network devices and, based onthe range value, indicates to the first network device an appropriate,and potentially lower, data rate for subsequent data transmission to thesecond network device. The second network device may also considerbattery parameter information received from the first network device anduse that information along with the range value to indicate to the firstnetwork device an appropriate power level, as well as data rate, forsubsequent transmissions by the first network device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a illustrates a warehouse environment incorporating acommunication network which maintains communication connectivity betweenthe various network devices according to the present invention.

FIG. 1 b illustrates other features of the present invention in the useof a mobile vehicle and an associated microLAN network which is capableof detaching from the main communication network when moving out ofrange of the main network to perform a service, and reattaching to themain network when moving within range to automatically report on theservices rendered.

FIG. 2 is a diagrammatic illustration of the use of a microLANsupporting roaming data collection by an operator according to thepresent invention.

FIG. 3 is a block diagram illustrating the functionality of RFtransceivers built in accordance with the present invention.

FIG. 4 is a diagrammatic illustration of an alternate embodiment of thepersonal microLAN shown in FIG. 2.

FIG. 5 is a block diagram illustrating a channel access algorithm usedby microLAN slave devices in according to the present invention.

FIG. 6 a is a timing diagram of the protocol used according to thepresent invention illustrating a typical communication exchange betweena microLAN master device having virtually unlimited power resources anda microLAN slave device.

FIG. 6 b is a timing diagram of the protocol used according to thepresent invention illustrating a typical communication exchange betweena microLAN master device having limited power resources and a microLANslave device.

FIG. 6 c is also a timing diagram of the protocol used which illustratesa scenario wherein the microLAN master device fails to service microLANslave devices.

FIG. 7 is a timing diagram illustrating the microLAN master device'sservicing of both the high powered main communication network and thelow powered microLAN subnetwork, with a single or plural radiotransceivers, in accordance with the present invention.

FIGS. 8 and 9 are block diagrams illustrating additional power savingfeatures according to the present invention wherein ranging and batteryparameters are used to optimally select the appropriate data rate andpower level of subsequent transmissions.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 a illustrates a warehouse environment incorporating acommunication network which maintains communication connectivity betweenthe various network devices according to the present invention.Specifically, a worker utilizes a computer terminal 7 and a code reader9 to collect data such as identifying numbers or codes on warehousedgoods, such as the box 10. As the numbers and codes are collected, theyare forwarded through the network to a host computer 11 for storage andcross-referencing. In addition, the host computer 11 may, for example,forward cross-referenced information relating to the collected numbersor codes back through the network for display on the terminal 7 or forprinting on a printer 13. Similarly, the collected may be printed fromthe computer terminal 7 directly to the printer 13. Other exemplarycommunication pathways supported by the present invention includemessages exchanged between the computer terminal 7 and other computerterminals (not shown) or the host computer 11.

Many of the devices found in the illustrative network are batterypowered and therefore must conservatively utilize their radiotransceivers. For example, the hand-held computer terminal 7 receivesits power from either an enclosed battery or a forklift battery (notshown) via a docking station within the forklift 14. Similarly, the codereader 9 operates on portable battery power as may the printer 13. Thearrangement of the communication network, communication protocols used,and data rate and power level adjustments help to optimize batteryconservation without substantially degrading network performance.

The overall communication network of the present invention is arrangedinto two functional groups: 1) a main communication network; and 2) amicroLAN network. The main communication network in the illustratedwarehouse embodiment includes a hard-wired backbone LAN 19 and basestations 15 and 17. A host computer 11 and any other non-mobile networkdevice located in the vicinity of the backbone LAN 19 can be directlyattached to the backbone LAN 19. However, mobile devices and remotelylocated devices must maintain connectivity to the backbone LAN 19through either a single base station such as the base station 15, orthrough a multi-hop network of base stations such as is illustrated bythe base stations 15 and 17. The base stations 15 and 17 contain ahigher power transmitter, and provide coverage over the entire warehousefloor. Although a single base station may be sufficient, if thewarehouse is too large or contains interfering physical barriers, themulti-hop plurality of base stations 17 may be necessary. Otherwise, thebackbone LAN 19 must be extended to connect all of the base stations 17directly to provide sufficient radio coverage. Through the maincommunication network, relatively stable, long range wireless andhard-wired communication is maintained.

Network devices that are mobile or remote (i.e., cannot be directlyconnected to the backbone LAN 19) are fitted with RF transceivers. Toguarantee that such a network device will be able to directlycommunicate with at least one of the base stations 15 and 17, the fittedtransceiver is selected to yield approximately the same transmissionpower as do the base stations 15 and 17. However, not all mobile orremote network devices require a direct RF link to the base stations 15and 17, and some may not require any link at all. Instead, communicationis generally localized to a small area and, as such, only requiresrelatively lower power, short range transceivers. The devices whichparticipate in the localized, short range communication, form what istermed herein a “microLAN”. For example, the interaction betweenperipheral devices such as the printer 13, modem 23, and code reader 9with the terminal 7 provide a justification for a microLANconfiguration.

For example, the printer 13 may be located in a dock with the soleassignment of printing out forms based on the code information gatheredfrom boxes delivered to the dock. In such an example, only when theforklift 14 enters the dock area should the printer 13 begin printingthe collected code information. Within the dock area, communicating viathe base stations 15 and 17 with the required high powered transceiversis avoided by establishing a microLAN on the dock. Specifically, insteadof the high powered transceivers for communicating with the maincommunication network, the printer 13 is fitted with a low powermicroLAN transceiver for short range communication directly to thecomputer terminal 7 in the forklift 14. The computer terminal 7 is alsofitted with a transceiver capable of direct, low power communicationwith the printer 13. Thus, when within microLAN radio range of theprinter 13, the computer terminal 7 transmits the code information at arelatively low power level to the printer 13. While in range (whetherprinting or not), the computer terminal 7 and printer 13 togetherparticipate in a low power, microLAN network.

In the previous example, no communication was necessary between themicroLAN devices and the main network. However, other microLANconfigurations require at least some access to the main network. Forexample, because of battery constraints, the code reader 9 is alsofitted with a microLAN transceiver. Whenever the code reader 9 is used,collected code signals and counterpart information are not directlyexchanged with the host computer 11 via the main network. Instead, inthe illustrated example, the computer terminal 7 is configured to beable to communicate not only within the microLAN but also through themain communication network. This is accomplished by fitting the computerterminal 7 with a transceiver(s) capable of communicating on bothnetworks (see discussion related to FIG. 3 below). Thus, to reach thehost computer 11, the code reader 9 first transmits to the computerterminal 7 via the microLAN, i.e., through the microLAN transceivers ineach device. Upon receipt of the data, the computer terminal 7 relaysthe information to one of the base stations 15 and 17 for forwarding tothe host 11. Communication from the host 11 to the code reader 9 isaccomplished via the same pathway.

It is also possible for any two devices in the microLAN network tocommunicate to each other. For example, the modem 23 could receive dataand directly transmit it to the printer 13 for printing. Similarly, thecode reader 9 might choose to directly communicate code signals to othernetwork devices via the modem 23.

In an alternate configuration, a microLAN base station 21 is providedwhich may be directly connected to the backbone LAN 19 (as shown) orindirectly connected via the base stations 15 and 17. The microLAN basestation 21 is positioned in the vicinity of a other microLAN networkdevices and thereafter becomes a participant. Thus, microLANcommunication flowing to or from the main communication network avoidshigh power radio transmissions altogether. However, it can beappreciated that a stationary microLAN base station may not always be anoption when all of the microLAN participants are mobile. In such cases,a high power transmission to reach the main communication network may berequired.

As briefly described above, in any microLAN, the participating devices(“microLAN devices”) need not all possess the transceiver capability toreach the main communication network. However, at least one microLANdevice needs to have that capability to maintain overall networkconnectivity.

FIG. 1 b illustrates other features of the present invention in the useof a mobile vehicle and an associated microLAN network which is capableof detaching from the main communication network when moving out ofrange of the main network to perform a service, and reattaching to themain network when moving within range to automatically report on theservices rendered. In particular, like the forklift 14 of FIG. 1 a, adelivery truck 33 provides a focal point for microLAN access. Within thetruck 33, a storage terminal 31 is docked so as to draw power from thetruck 33's battery supply. The storage terminal 31 is configured with amicroLAN transceiver. Similarly, a computer terminal 7 also configuredas a microLAN device may either be docked or ported. Because of greaterbattery access and because of the amount of data to transfer, thestorage terminal 31 is also configured to communicate with the maincommunication network.

Prior to making a delivery, the truck enters a docking area for loading.As goods are loaded into the truck, the driver enters informationregarding each loaded good into the storage terminal 31 via either theterminal 7 or the code reader 9 (FIG. 1 a) using the microLAN networkcommunications. This loading might also be accomplished automatically asthe forklift 14 comes into range of the delivery truck 31, joins themicroLAN network, and transmits the previously collected data asdescribed above in relation to FIG. 1 a. In addition, as informationregarding a good is received and stored, the storage device might alsorequest further information regarding any or all of the goods via themicroLAN's link to the host computer 11 through the main communicationnetwork. Specifically, the microLAN base station 21 if located on thedock could provide a direct low power microLAN connection to thebackbone LAN 19 and to the host computer 11. Otherwise, because of thenormal data flow pathway and because of its greatest access to availablepower, the storage terminal 31 is configured with a transceiver capableof communicating with the main communication network via the basestations 15 and 17. When fully loaded and prior to leaving the dock, thestorage device 31 communicates via the microLAN to the printer 13 togenerate a printout of information relating to the loaded goods. Inaddition, the information is transmitted via the microLAN to the modem23 for relay to a given destination site. Upon reaching the destination,the storage terminal 31 detects and participates in the microLAN of thedelivery site dock. As goods specific goods are unloaded, they arescanned for delivery verification, preventing delivery of unwantedgoods. The driver is also informed if goods that should have beendelivered are still in the truck. As this process takes place, a reportmight also be generated via a microLAN printer on the destination dockfor signature. Similarly, a microLAN modem on the destination dock mightrelay the delivery information back to the host computer 11 for billinginformation.

Similarly, if the truck 33 is used for service purposes, the truck 33leaves the dock in the morning with the addresses and directions of theservice destinations, technical manuals, and service notes which havebeen selectively downloaded from the host computer via the main networkand microLAN to the storage terminal 31. Upon pulling out of range ofthe microLAN network in the dock, the storage terminal 31 and thecomputer terminal 7 automatically form an independent, detachedmicroLAN. At each service address, the driver collects information usingthe terminal 7 either as the data is collected if within microLANtransmission range of the storage terminal 31, or as soon as theterminal 7 comes within range. Through the detached microLAN networksuch information is available on the computer terminal. Upon returningto the dock, as soon as the independent microLAN formed between thestorage terminal 31 and the computer terminal 7 come within microLANrange of the microLAN devices on the dock, the detached microLANautomatically merges with the dock's microLAN (becomes “attached”), andthe storage terminal 31 automatically transfers the service informationto the host computer 11 which uses the information for billing and informulating the service destinations which will be automaticallydownloaded the next day.

FIG. 2 is a diagrammatic illustration of another embodiment using amicroLAN to supporting roaming data collection by an operator accordingto the present invention. As an operator 61 roams the warehouse floor hecarries with him a microLAN comprising the terminal 7, code reader 9 anda portable printer 58. The operator collect information regarding goods,such as the box 10, with the code reader 9 and the terminal 7. If thepower resources are equal, the terminal 7 may be designated to alsocommunicate with the main communication network. Specifically,corresponding information to the code data must be retrieved from thehost computer 11, collected code information and retrieved correspondinginformation needs to be displayed on the terminal 7, and, after viewingfor verification, the information needs to be printed on the printer 58.Because of this data flow requirement, the computer terminal 7 isselected as the microLAN device which must also carry the responsibilityof communicating with the main communication network.

If during collection, the operator decides to power down the computerterminal 7 because it is not needed, the microLAN network becomesdetached from the main communication network. Although it might bepossible for the detached microLAN to function, all communication withthe host computer 11 through the main communication network is placed ina queue awaiting reattachment. As soon as the detached microLAN comeswithin range of an attached microLAN device, i.e., a device attached tothe main network, the queued communications are relayed to the host.

To avoid detachment when the terminal 7 is powered down, the code reader9 may be designated as a backup to the terminal 7 for performing thehigher power communication to the main communication network. Asdescribed in more detail below in reference to FIG. 6 c regarding theidle sense protocol, whenever the code reader 9 determines that theterminal 7 has stopped providing access to the main communicationnetwork, the code reader 9 will take over the role if it is next in lineto perform the backup service. Thereafter, when the computer terminal 7is powered up, it monitors the microLAN channel, requests and regainsfrom the code reader 9 the role of providing an interface with the maincomputer network. This, however, does not restrict the code reader 9from accessing the main computer network although the reader 9 maychoose to use the computer terminal 7 for power conservation reasons.

In addition, if the computer terminal 7 reaches a predetermined lowbattery threshold level, the terminal 7 will attempt to pass the burdenof providing main network access to other microLAN backup devices. If nobackup device exists in the current microLAN, the computer terminal 7may refuse all high power transmissions to the main communicationnetwork. Alternatively, the computer terminal 7 may either refusepredetermined select types of requests, or prompt the operator beforeperforming any transmission to the main network. However, the computerterminal 7 may still listen to the communications from the maincommunication network and inform microLAN members of waiting messages.

FIG. 3 is a block diagram illustrating the functionality of RFtransceivers built in accordance with the present invention. Althoughpreferably plugging into PCMCIA slots of the computer terminals andperipherals, the transceiver 110 may also be built-in or externallyattached via available serial, parallel or ethernet connectors forexample. Although the transceivers used by potential microLAN masterdevices may vary from those used by microLAN slave devices (as detailedbelow), they all contain the illustrated functional blocks.

In particular, the transceiver 110 contains a radio unit 112 whichattaches to an attached antenna 113. The radio unit 112 used in microLANslave devices need only provide reliable low power transmissions, andare designed to conserve cost, weight and size. Potential microLANmaster devices not only require the ability to communicate with microLANslave devices, but also require higher power radios to also communicatewith the main network. Thus, potential microLAN master devices and othernon-microLAN slave devices might contain two radio units 112 (or twotransceivers 110)—one serving the main network and the other serving themicroLAN network—else only contain a single radio unit to service bothnetworks.

In embodiments where cost and additional weight is not an issue, a dualradio unit configuration for potential microLAN master devices providesseveral advantages. For example, simultaneous transceiver operation ispossible by choosing a different operating band for each radio. In suchembodiments, a 2.4 GHz radio is included for main network communicationwhile a 27 MHz radio supports the microLAN network. MicroLAN slavedevices receive only the 27 MHz radio, while the non-potential microLANparticipants from the main network are fitted with only the 2.4 GHzradios. Potential microLAN master devices receive both radios. The lowpower 27 MHz microLAN radio is capable of reliably transferringinformation at a range of approximately 40 to 100 feet asynchronously at19.2K BPS. An additional benefit of using the 27 MHz frequency is thatit is an unlicensed frequency band. The 2.4 GHz radio providessufficient power (up to 1 Watt) to communicate with other main networkdevices. Many different frequency choices could also be made such as the900 MHz band, etc.

In embodiments where cost and additional weight are at issue, a singleradio unit configuration is used for potential microLAN master devices.Specifically, in such embodiments, a dual mode 2.4 GHz radio supportsboth the microLAN and main networks. In a microLAN mode, the 2.4 GHzradio operates at a low power level (sub-milliwatt) to support microLANcommunication at relatively close distances (20-30 feet). In a highpower (up to 1 Watt) or main mode, the 2.4 GHz radio provides relativelylong distance communication connectivity with the main network. Althoughall network devices might be fitted with such a dual mode radio, onlymicroLAN master devices use both modes. MicroLAN slave devices wouldonly use the low power mode while all other main network devices woulduse only the high power mode. Because of this, to save cost, microLANslave devices are fitted with a single mode radio operating in themicroLAN mode. Non-microLAN participants are also fitted with a singlemode (main mode) radio unit for cost savings.

Connected between the radio unit 112 and an interface 110, amicroprocessor 120 controls the information flow between through thetransceiver 110. Specifically, the interface 115 connects thetransceiver 110 to a selected computer terminal, a peripheral device orother network device. Many different interfaces 115 are used and thechoice will depend upon the connection port of the device to which thetransceiver 110 will be attached. Virtually any type of interface 110could be adapted for use with the transceiver 110 of the presentinvention. Common industry interface standards include RS-232, RS-422,RS-485, 10BASE2 Ethernet, 10BASE5 Ethernet, 10BASE-T Ethernet, fiberoptics, IBM 4/16 Token Ring, V.11, V.24, V.35, Apple Localtalk andtelephone interfaces. In addition, via the interface 115, themicroprocessor 120 maintains a radio independent, interface protocolwith the attached network device, isolating the attached device from thevariations in radios being used.

The microprocessor 120 also controls the radio unit 112 to accommodatecommunication with the either the main network (for main mode radios),the microLAN (for microLAN radios), or both (for dual mode radios). Morespecifically, in a main mode transceiver, the microprocessor 120utilizes a main protocol to communicate with the main network.Similarly, in a microLAN mode transceiver, the microprocessor 120operates pursuant to a microLAN protocol to communicate in the microLANnetwork. In the dual mode transceiver, the microprocessor 120 managesthe use of and potential conflicts between both the main and microLANprotocols. Detail regarding the main and microLAN protocols can be foundin reference to FIGS. 6-9 below.

In addition, as directed by the corresponding communication protocol,the microprocessor 120 controls the power consumption of the radio 112,itself and the interface 115 for power conservation. This isaccomplished in two ways. First, the microLAN and main protocols aredesigned to provide for a low power mode or sleep mode during periodswhen no communication involving the subject transmitter is desired asdescribed below in relation to FIGS. 6-7. Second, both protocols aredesigned to adapt in both data rate and transmission power based onpower supply (i.e., battery) parameters and range information asdescribed in reference to FIGS. 8-9.

In order to insure that the proper device is receiving the informationtransmitted, each device is assigned a unique address. Specifically, thetransceiver 110 can either have a unique address of its own or can usethe unique address of the device to which it is attached. The uniqueaddress of the transceiver can either be one selected by the operator orsystem designer or one which is permanently assigned at the factory suchas an IEEE address. The address 121 of the particular transceiver 110 isstored with the microprocessor 120.

In the illustrated embodiments of FIGS. 1-2, the microLAN master deviceis shown as being either a microLAN base station or a mobile or portablecomputer terminal. From a data flow viewpoint in considering the fastestaccess through the network, such choices for the microLAN master devicesappear optimal. However, any microLAN device might be assigned the roleof the master, even those that do not seem to provide an optimal dataflow pathway but may provide for optimal battery usage. For example, inthe personal microLAN network of FIG. 2, because of the support from thebelt 59, the printer might contain the greatest battery capacity of thepersonal microLAN devices. As such, the printer might be designated themicroLAN master device and be fitted with either a dual mode radio ortwo radios as master devices require. The printer, or other microLANslave devices, might also be fitted with such required radios to serveonly as a microLAN master backup. If the battery power on the actualmicroLAN master, i.e., the hand-held terminal 7 (FIG. 2), drops below apreset threshold, the backup master takes over.

FIG. 4 is a drawing which illustrates an embodiment of the personalmicroLAN shown in FIG. 2 which designates a printer as the microLANmaster device. Specifically, in a personal microLAN network 165, acomputer terminal 170 is strapped to the forearm of the operator. A codereader 171 straps to the back of the hand of the user and is triggeredby pressing a button 173 with the thumb. Because of their relatively lowbattery energy, the computer terminal 170 and code reader 171 aredesignated microLAN slave devices and each contain a microLANtransceiver having a broadcast range of two meters or less. Because ofits greater battery energy, the printer 172 contains a dual mode radioand is designated the microLAN master device.

FIG. 5 is a block diagram illustrating a channel access algorithm usedby microLAN slave devices in according to the present invention. At ablock 181, when a slave device has a message to send, it waits for anidle sense message to be received from the microLAN master device at ablock 183. When an idle sense message is received, the slave deviceexecutes a back-off protocol at a block 187 by in an attempt to avoidcollisions with other slave devices waiting to transmit. Basically,instead of permitting every slave device from repeatedly transmittingimmediately after an idle sense message is received, each waiting slaveis required to first wait for a pseudo-random time period beforeattempting a transmission. The pseudo-random back-off time period isgenerated and the waiting takes place at a block 187. At a block 189,the channel is sensed to determine whether it is clear for transmission.If not, a branch is made back to the block 183 to attempt a transmissionupon receipt of the next idle sense message. If the channel is stillclear, at a block 191, a relatively small “request to send” type packetis transmitted indicating the desire to send a message. If no responsive“clear to send” type message is received from the master device, theslave device assumes that a collision occurred at a block 193 andbranches back to the block 183 to try again. If the “clear to send”message is received, the slave device transmits the message at a block195.

Several alternate channel access strategies have been developed forcarrier sense multiple access (CSMA) systems and include 1-persistent,non-persistent and p-persistent. Such strategies or variations thereofcould easily be adapted to work with the present invention.

FIG. 6 a is a timing diagram of the protocol used according to thepresent invention illustrating a typical communication exchange betweena microLAN master device having virtually unlimited power resources anda microLAN slave device. Time line 201 represents communication activityby the microLAN master device while time line 203 represents thecorresponding activity by the microLAN slave device. The masterperiodically transmits an idle sense message 205 indicating that it isavailable for communication or that it has data for transmission to aslave device. Because the master has virtually unlimited powerresources, it “stays awake” for the entire time period 207 between theidle sense messages 205. In other words, the master does not enter apower conserving mode during the time periods 207.

The slave device uses a binding protocol (discussed below with regard toFIG. 6 c) to synchronize to the master device so that the slave mayenter a power conserving mode and still monitor the idle sense messagesof the master to determine if the master requires servicing. Forexample, referring to FIG. 6 a, the slave device monitors an idle sensemessage of the master during a time period 209, determines that noservicing is required, and enters a power conserving mode during thetime period 211. The slave then activates during a time period 213 tomonitor the next idle sense message of the master. Again, the slavedetermines that no servicing is required and enters a power conservingmode during a time period 215. When the slave activates again during atime period 217 to monitor the next idle sense message, it determinesfrom a “request to send” type message from the master that the masterhas data for transmission to the slave. The slave responds by sending a“clear to send” type message during the time period 217 and staysactivated in order to receive transmission of the data. The master isthus able to transmit the data to the slave during a time period 219.Once the data is received by the slave at the end of the time period221, the slave again enters a power conserving mode during a time period223 and activates again during the time period 225 to monitor the nextidle sense message.

Alternatively, the slave may have data for transfer to the master. Ifso, the slave indicates as such to the master by transmitting a messageduring the time period 217 and then executes a backoff algorithm todetermine how long it must wait before transmitting the data. The slavedetermines from the backoff algorithm that it must wait the time period227 before transmitting the data during the time period 221. The slavedevices use the backoff algorithm in an attempt to avoid the collisionof data with that from other slave devices which are also trying tocommunicate with the master. The backoff algorithm is discussed morefully above in reference to FIG. 5.

The idle sense messages of the master may also aid in schedulingcommunication between two slave devices. For example, if a first slavedevice has data for transfer to a second slave device, the first slavesends a message to the master during the time period 209 requestingcommunication with the second slave. The master then broadcasts therequest during the next idle sense message. Because the second slave ismonitoring the idle sense message, the second slave receives the requestand stays activated at the end of the idle sense message in order toreceive the communication. Likewise, because the first slave is alsomonitoring the idle sense message, it too receives the request and staysactivated during the time period 215 to send the communication.

FIG. 6 b is a timing diagram of the protocol used according to thepresent invention illustrating a typical communication exchange betweena microLAN master having limited power resources and a microLAN slavedevice. This exchange is similar to that illustrated in FIG. 6 a exceptthat, because it has limited power resources, the master enters a powerconserving mode. Before transmitting an idle sense message, the masterlistens to determine if the channel is idle. If the channel is idle, themaster transmits an idle sense message 205 and then waits a time period231 to determine if any devices desire communication. If nocommunication is desired, the master enters a power conserving modeduring a time period 233 before activating again to listen to thechannel. If the channel is not idle, the master does not send the idlesense message and enters a power saving mode for a time period 235before activating again to listen to the channel.

Communication between the master and slave devices is the same as thatdiscussed above in reference to FIG. 6 a except that, after sending orreceiving data during the time period 219, the master device enters apower conserving mode during the time period 237.

FIG. 6 c is also a timing diagram of the protocol used which illustratesa scenario wherein the microLAN master device fails to service microLANslave devices. The master device periodically sends an idle sensemessage 205, waits a time period 231, and enters a power conserving modeduring a time period 233 as discussed above in reference to FIG. 6 b.Similarly, the slave device monitors the idle sense messages during timeperiods 209 and 213 and enters a power conserving mode during timeperiods 211 and 215. For some reason, however, the master stopstransmitting idle sense messages. Such a situation may occur, forexample, if the master device is portable and is carried outside therange of the slave's radio. During a time period 241, the slaveunsuccessfully attempts to monitor an idle sense message. The slave thengoes to sleep for a time period 243 and activates to attempt to monitora next idle sense message during a time period 245, but is againunsuccessful.

The slave device thereafter initiates a binding protocol to attempt toregain synchronization with the master. While two time periods (241 and245) are shown, the slave may initiate such a protocol after any numberof unsuccessful attempts to locate an idle sense message. With thisprotocol, the slave stays active for a time period 247, which is equalto the time period from one idle sense message to the next, in anattempt to locate a next idle sense message. If the slave is againunsuccessful, it may stay active until it locates an idle sense messagefrom the master, or, if power consumption is a concern, the slave mayenter a power conserving mode at the end of the time period 247 andactivate at a later time to monitor for an idle sense message.

In the event the master device remains outside the range of the slavedevices in the microLAN network for a period long enough such thatcommunication is hindered, one of the slave devices may take over thefunctionality of the master device. Such a situation is useful when theslave devices need to communicate with each other in the absence of themaster. Preferably, such a backup device has the ability to communicatewith devices on the main communication network. If the original masterreturns, it listens to the channel to determine idle sense messages fromthe backup, indicates to the backup that it has returned and then beginsidle sense transmissions when it reestablishes dominance over themicroLAN network.

FIG. 7 is a timing diagram illustrating the microLAN master device'sservicing of both the high powered main communication network and thelow powered microLAN subnetwork, with a single or plural radiotransceivers, in accordance with present invention. Block 251 representstypical communication activity of the master device. Line 253illustrates the master's communication with a base station on the maincommunication network while line 255 illustrates the master'scommunication with a slave device on the microLAN network. Lines 257 and259 illustrate corresponding communication by the base station and slavedevice, respectively.

The base station periodically broadcasts HELLO messages 261 indicatingthat it is available for communication. The master device monitors theHELLO messages during a time period 263, and, upon determining that thebase does not need servicing, enters a power conserving mode during atime period 265. The master then activates for a time period to monitorthe next HELLO message from the base. If the master has data to send tothe base, it transmits the data during a time period 271. Likewise, ifthe base has data to send to the master, the base transmits the dataduring a time period 269. Once the data is received or sent by themaster, it may again enter a power conserving mode. While HELLO messageprotocol is discussed, a number of communication protocols may be usedfor communication between the base and the master device. As may beappreciated, the microLAN master device acts as a slave to base stationsin the main communication network.

Generally, the communication exchange between the master and the slaveis similar to that described above in reference to FIG. 6 b. Block 273,however, illustrates a situation where the master encounters acommunication conflict, i.e., it has data to send to or receive from theslave on the subnetwork at the same time it will monitor the mainnetwork for HELLO messages from the base. If the master has two radiotransceivers, the master can service both networks. If, however, themaster only has one radio transceiver, the master chooses to service onenetwork based on network priority considerations. For example, in block273, it may be desirable to service the slave because of the presence ofdata rather than monitor the main network for HELLO messages from thebase. On the other hand, in block 275, it may be more desirable tomonitor the main network for HELLO messages rather than transmit an idlesense message on the subnetwork.

FIGS. 8 and 9 are block diagrams illustrating additional power savingfeatures according to the present invention, wherein ranging and batteryparameters are used to optimally select the appropriate data rate andpower level for subsequent transmissions. Specifically, even thoughnetwork devices such as the computer terminal 7 in FIGS. 1-2 have thecapability of performing high power transmissions, because of batterypower concerns, the such devices are configured to utilize minimumtransmission energy. For example if By adjusting either the power leveland the data rate based. Adjustments are made based on ranginginformation and on battery parameters. Similarly, within the microLANnetwork, even though lower power transceivers are used, batteryconservation issues also justify the use such data rate and poweradjustments. This process is described in more detail below in referenceto FIGS. 8 and 9.

More specifically, FIG. 8 is a block diagram which illustrates aprotocol 301 used by a destination microLAN device and a correspondingprotocol 303 used by a source microLAN device to adjust the data rateand possibly the power level for future transmission between the twodevices. At a block 311, upon receiving a transmission from a sourcedevice, the destination device identifies a range value at a block 313.In a low cost embodiment, the range value is identified by consideringthe received signal strength indications (RSSI) of the incomingtransmission. Although RSSI circuitry might be placed in all microLANradios, the added expense may require that only microLAN master devicesreceive the circuitry. This would mean that only microLAN master deviceswould perform the function of the destination device. Other rangingvalues might also be calculated using more expensive techniques such asadding GPS (Global Position Service) circuitry to both radios. In suchan embodiment, the range value transmitted at the block 313 wouldconsist of the GPS position of the destination microLAN device. Finally,after identifying the range value at the block 313, the destinationdevice subsequently transmits the range value to the slave device fromwhich the transmission was received.

Upon receipt of the range value from the destination device at a block321, the source microLAN device evaluates its battery parameters toidentify a subsequent data rate for transmission at a block 323. Ifrange value indicates that the destination microLAN device is very near,the source microLAN device selects a faster data rate. When the rangevalue indicates a distant master, the source device selects a slowerrate. In this way, even without adjusting the power level, the totalenergy dissipated can be controlled to utilize only that necessary tocarry out the transmission. However, if constraints are placed on themaximum or minimum data rates, the transmission power may also need tobe modified. For example, to further minimize the complexity associatedwith a fully random range of data rate values, a standard range and setof several data rates may be used. Under such a scenario, a transmissionpower adjustment might also need to supplement the data rate adjustment.Similarly, any adjustment of power must take into consideration maximumand minimum operable levels. Data rate adjustment may supplement suchlimitations. Any attempted modification of the power and data rate mighttake into consideration any available battery parameters such as thosethat might indicate a normal or current battery capacity, the drain onthe battery under normal conditions and during transmission, or the factthat the battery is currently being charged. The latter parameter provesto be very significant in that when the battery is being charged, themicroLAN slave device has access to a much greater power source fortransmission, which may justify the highest power transmission andpossibly the slowest data rate under certain circumstances.

Finally, at a block 325, an indication of the identified data rate istransmitted back to the destination device so that future transmissionsmay take place at the newly selected rate. The indication of data ratemay be explicit in that a message is transmitted designating thespecific rate. Alternately, the data rate may be transferee implicitlyin that the new rate is chose and used by the source, requiring thedestination to adapt to the change. This might also be done using apredefined header for synchronization.

FIG. 9 illustrates an alternate embodiment for carrying out the datarate and possibly power level adjustment. At a block 351 upon bindingand possibly periodically, the source microLAN device sends anindication of its current battery parameters to the destination microLANdevice. This indication may be each of the parameters or may be anaveraged indication of all of the parameters together. At a block 355,upon receipt, the destination microLAN device 355 stores the batteryparameters (or indication). Finally, at a block 358, upon receiving atransmission from the source device, based on range determinations andthe stored battery parameters, the destination terminal identifies thesubsequent data rate (and possibly power level). Thereafter, the newdata rate and power level are communicated to the source device foreither explicitly or implicitly for future transmissions.

Moreover, it will be apparent to one skilled in the art having read theforegoing that various modifications and variations of thiscommunication system according to the present invention are possible andis intended to include all those which are covered by the appendedclaims.

1-9. (canceled)
 10. A method of determining a location of a firstwireless communication device, comprising: receiving a wirelesscommunication signal at the device; determining a strength of thereceived signal; and generating an indication of a location of thedevice based on the strength of the received signal.
 11. The method ofclaim 10 further comprising performing a function based on theindication of the location of the device.
 12. The method of claim 10further comprising transmitting the determined strength of the receivedsignal to a second wireless communication device, and wherein the seconddevice generates the indication of the location of the first devicebased on the determined strength of the received signal.
 13. The methodof claim 12 wherein the second device is the device that transmitted thewireless communication signal received at the first device.
 14. Themethod of claim 12 wherein the second device has a fixed location. 15.The method of claim 12 wherein the first device is operable to serve asa master device relative to the second device, and the second device isoperable to serve as a slave device relative to the first device. 16.The method of claim 15 wherein the first device is operable to performcontrol functions controlling aspects of communications of the seconddevice.
 17. The method of claim 12 further comprising the second deviceperforming a function based on the indication of the location of thefirst device.
 18. The method of claim 12 further comprising the seconddevice executing an application that uses the indication of the locationof the first device.
 19. The method of claim 10 wherein determining thestrength of the received signal comprises generating a received signalstrength indicator (RSSI).
 20. The method of claim 10 further comprisingtransmitting the indication of the location of the first device to asecond wireless communication device.
 21. The method of claim 20 whereinthe second device is the device that transmitted the wirelesscommunication signal received at the first device.
 22. The method ofclaim 20 wherein the second device has a fixed location.
 23. The methodof claim 20 further comprising the second device performing a functionbased on the indication of the location of the first device.
 24. Themethod of claim 20 further comprising the second device executing anapplication that uses the indication of the location of the firstdevice.
 25. The method of claim 10 wherein the first device is a mobiledevice.
 26. The method of claim 10 further comprising generating anindication of the location of the device using a global navigationsatellite system.
 27. The method of claim 10 wherein the indication of alocation of the device comprises a range value representative of adistance between the first device and a second wireless communicationdevice that transmitted the wireless communication signal received atthe first device.
 28. A wireless communication device transceiver,comprising: a receiver operable to receive a wireless communicationsignal; a control unit operable to determine a strength of the receivedsignal and operable to generate an indication of a location of thedevice based on the strength of the received signal.
 29. The transceiverof claim 28 wherein the control unit is further operable to perform afunction based on the indication of the location of the device.
 30. Thetransceiver of claim 28 further comprising a transmitter, wherein thetransceiver resides in a first wireless communication device and whereinthe control unit is operable to cause the transmitter to transmit thedetermined strength of the received signal to a second wirelesscommunication device.
 31. The transceiver of claim 30 wherein the seconddevice is a device that transmitted the wireless communication signalreceived by the first device.
 32. The transceiver of claim 30 whereinthe second device has a fixed location.
 33. The transceiver of claim 30wherein the first device is operable to serve as a master devicerelative to the second device, and the second device is operable toserve as a slave device relative to the first device.
 34. Thetransceiver of claim 33 wherein the control unit is operable to performcontrol functions controlling aspects of communications of the seconddevice.
 35. The transceiver of claim 28 wherein the control unit isoperable to generate a received signal strength indicator (RSSI). 36.The transceiver of claim 28 further comprising a transmitter, whereinthe transceiver resides in a first wireless communication device andwherein the control unit is operable to cause the transmitter totransmit the indication of the location of the first device to a secondwireless communication device.
 37. The transceiver of claim 36 whereinthe second device is a device that transmitted the wirelesscommunication signal received by the first device.
 38. The transceiverof claim 36 wherein the second device has a fixed location.
 39. Thetransceiver of claim 28 wherein the transceiver resides in a mobiledevice.
 40. The transceiver of claim 28 further comprising globalnavigation satellite system functionality operable to generate anindication of the location of the device.
 41. The transceiver of claim28 wherein the indication of a location of the device comprises a rangevalue representative of a distance between the first device and a secondwireless communication device that transmitted the wirelesscommunication signal received by the first device.